<html>
<head>
    <title>circle</title>
    <style type="text/css" >
        .circle 
        {  
            border-radius:50%; 
            background:#DDDDDD; 
        }
        .circle_inside 
        { 
            width:80%; 
            height:80%;
            left:10%; 
            border-radius:50%; 
            background:#494949;
            position:relative;
            top:10%;
        }
        #circle 
        {
            margin-left:50%;
            position:relative;
            left:-250px;
            width:500px;
            height:500px;
        }
    </style>
    <script type="text/javascript" >
        var c = 'DDDDDD,DFEFFF,494949,C8DB74,46DFDE,59DDDE'.split(',');
        function create_color() {
            var color = '',
                c_length = c.length,
                random_nmb = Math.floor(Math.random()*c_length);
            return '#'+c[random_nmb];
        }
        function create_inside_circle(color, id) {
            return "<div id='"+id+"' class='circle_inside' style='background:"+color+";'></div>";
        }
        function create_all_circle() {
            var circle_nmb = 15,
                html = [],
                id = 0,
                inside_circle = document.getElementById('circle');
            for(var i=0; i<circle_nmb; i++) {
                id = "circle"+i;
                inside_circle.innerHTML = create_inside_circle(create_color(), id);
                inside_circle = document.getElementById(id);
            }
        }   
        window.onload = function(){
            setInterval(function(){
                create_all_circle();
            }, 1500);
        }   
    </script> 
</head>
<body>
    <div class="circle bg1" id="circle">
    </div>
</body>
</html>